Mining system



Feb. 19; 1929.

L. F. CRAWFORD MINING SYSTEM 4 Sheets-Sheet l 'II 1 s Filed March 1928Feb. 19, 1929.

L. F. CRAWFORD I MINING SYSTEM 1928 4 Sheets-Sheet 2 Filed March 5,

-1111- i wmfi m U I k: \m 5 M 1. a a H 2 Feb. 19, 1929." 1,702,558

' L. F. CRAWF'ORD MINING SYSTEM Filed March 5, 1928 4 Sheets-Sheet 5M/iibrzzw Feb. 19, 1929;

L. F. CRAWFORD MINING SYSTEM Filed March 5, 1928 4 Sheets-Sheet 4Patented Feb. 19, 1929.

UNITED STATES 1,702,558 PATENT OFFICE.

LOYAL F. CRAWFORD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR T GOODMANMANUFACTURING'COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

MINING SYSTEM.

Application filed March 3, 1928.

This invention relates to improvements in mining systems, and moreparticularly to mining systems used for advancing double entries inrelatively thin or low coal seams, and has for its principal object toprovide an improved form of apparatus and system for driving in advancedevelopment work as for instance, in room and pillar mines, whereby therequirementof a certain skilled labor ordinarily employed in similaroperations is eliminated, brushing of the roof or taking of bottom andtransportation of waste rock resulting therefrom is reduced to aminimum, and the problem of suflicient mine carsupply is effectivelysolved in connection with the use of portable miningand scraperloadingdevices so that the costs of production of coal in relatively low seamsmay be reduced sufficiently to enable such thin seamed coal mines to beoperated in competition with higher seamed coal mines. v

I t is well'known that the constant demand for coal is causing aconstant diminution of ill the available supply in themines where thecoal measures are thick or high enough to permit the use of standardmining apparatus and transportation facilities including mine cars,without requiring the removal of excess rock above or below the haulageways and mine tracks. Such relatively high coal measures aregenerallytermedhigh coalof which the minimum height is usuallyconsidered to be about three and one-half or four feet. The diminutionin the available supply of such high coal has resulted in an increasingdevelopment of relatively low coal mines, where the coal seams are lessthan three and one-half to four feet in thickness, although the costs ofcoal extraction naturally tend to exceed the costs of extraction of thehigher coal on account of the added difficulties imposed by low roofconditions. In some instances the added cost of mining'low coal ispartially offset by the fact that the coal is of better grade, or thatthe mine is nearer the point of consumption than a competing hi gh coalmine, but in every case the success ful operation of relatively low coalmines depends mainly upon the development of a highly improvedeconomical mining system which will enable such mines to overcome theirinherent disadvantages and compete upon a fairly equitable basis withhigh coal mines.

Accordingly, it will be borne in mind, in

Serial No. 258,728.

connection with the following description of my invention, that theimproved mining system and apparatus has been developed with especialreference to the difficulties imposed by low roof conditions, where atleast a port-ion of the rock roof or floor must be removed to permit theuse of standard equipment including mine cars of standard height,although it will be understood further that many of the features hereindisclosed are not necessarily limited to low roof conditions but mayalso have general application to other systems of mining.

The invention may best be understood by reference to the accompanyingdrawings in which:

Figure 1 is a plan view of a double entry advance development, withparts of the entries broken away at certain points as indicated, andshowing the arrangement of the tracks in one stage of development;

Figure 2 is a view similar to Figure 1 but showing the advance work inanother stage of development with the coal cutting and loading appartusin operative position and with a string of mine cars on the tracks;

Figure 3 is a vertical section taken on line 38 of Figure 2,- t

Figure 4: is a vertical section taken on line 4+4 of Figure 2;

, Figure 5 is a view similar to Figure 2 but showing a cutting andloading apparatus in a further advanced stage of operation;

Figure 6 is an enlarged detail view of an improved form of a portion oftrack made up in detachable sections, which is utilized as a part of myimproved mining system;

Figure 7 is a view of another portion of track forming'a part of myimproved mining apparatus;

Figure 8 is a view similar to Figure 5, showing analternativeintermediate step of mining out a complete break through fromone extended entry before work is begun upon the adjacent entry; and

' Figure 9 is a view similar to Figure 8 showing the alternativeintermediate step in further stage of advancement with mine tracksinstalled.

Referring now to the details of the mining system shown in the drawings,it will be understood that the principal object of the sys tem thereinshown is to advance a pair of entries 10 and 11, arranged in parallelrelationship. to each other and separated by a series of pillars 12, 12,having a plurality of break throughs 13, 13, forming transversepassageways at certain intervals between the parallel entries 10 and 11.The entries are driven in pairs in the usual manner so as to provideincoming and outgoing air passages forming part of the generalventilation system of the mine. The several break throughs 13, 13, alsoform a part of the ventilation system as required during the advancedevelopmental work, as well as providing communication between adjacententries for transportation purposes. The width of the entries 10 and 11may vary somewhat depending upon the local conditions but with theprefered sys-' tem herein illustrated they are of suflicient width fortrack haulage as well as turning radius on the track curves, for whichpurposes the entries should be in the neighborhood of twenty-four feetin width. The width of the pillars 12, 12, may also vary, depending uponlocal conditions, in the illustration shown the pillars beingapproximately sixteen feet in width. The length of the pillars,determined by the distance between the break throughs 13, 13, ispreferably as great as possible commensurate with requirements forventilation during advancing work, and also to permit the use ofrelatively long stretches of track as storage space for mine cars duringloading operations. In many States of the Union, the cutting of breakthroughs within certain defined limits of advance development is mandatory either by statute or mine regulations, these limits ranging fromone hundred to three hundred feet, provided that auxiliary ventilationmeans be utilized, as will hereinafter be described in greater detail.In carrying out my invention, I find it preferably to make the distancebetween the break throughs as long as permissible by law, a distance oftwo hundred to three hundred fifty being found preferable where localregulations and gas conditions permit.

The advancing of the two entries 10 and 11 from one break through 13 tothe next represents one complete cycle in the driving operations.

In order to describe a complete cycle of operations, it will benecessary to refer generally to some of the more important features ofarrangement of the entries, break throughs and trackage layed out duringprevious cycles of operation. Thus in Figure 1, a haulage track 1 1extends up one of the entries as for instance, the entry 11, adjacentits outer wall, which entry has, as shown in Figure 4, had its heightincreased over the normal height A-B of the coal measure by a distancesuificient to give clearance over the mine cars, as indicated at AC. Thewaste rock material, which in the system illustrated herein is taken orbrushed from the roof, has been previously disposed in areas indicatedat 12*, 12, at the opposite sides of the pillars 12, these areas beinggenerally referred to as the gob. These areas are preferably surroundedand defined by rows of mine props 12 of the usual type adapted to assistin supporting the roof adjacent the brushed areas. The haulage track 1 1extends forwardly to and through the lastbreak through 13 and is loopedbackwardly through the opposite entry 10 and the nest to the last breakthrough. 13, where it agam connects with the main haulage track 14 asclearly shown in Figure 1, thus forming a continuous loop about the nextto the last chain pillar 12, as indicated generally by the numeral 15.This track loop 15 is preferably made up of a plurality of detachabletrack sections, as will. hereinafter more fully appear. For the presentdescription it is sufiicient to call attention to the two stub tracks Tand T disposed on opposite sides and closely parallel to the last pillar12, beyond the loop 15. These track stubs are utilized for placing ofthe cutting and lcadingapp aratus as will presently be described.

The portions of the roof immediately above the break through 13 and thestubs T and T are also brushed to a height greater than the normalheight of the coal seam A E. as indicated at A@ in Figure 3. A loadingchute 23, forming part of the loading apparatus, is shown as mounted onthe truck section The working faces of the two entries, i. e., the faceswhich are to be advanced in order to prolong the entries, are indicatedat 16 and 17 respectively, and in the preferred form to be hereindescribed are each about twenty four feet wide. These working faces 16and 17 are disposed about fifty feet in advance of the last breakthrough 13, in order to provide a sufficient lead for the scraper loadercables, as will presently appear. It will be understood of course, thatthe lines along which mining operations are advanced, and the distancesbetween the points such as break throughs, track centers, etc, have allbeen previously de termined upon and laid out by careful survey.

With the arrangement of trackage and developmental work in the stageshown in Figure 1 the necessary undercutting and loading devices arebrought into the mining area on the haulage track 14. In the form shownthe apparatus referred to includes an undercutting machine 20 of theshortwall type and a truck 21 from which said machine is removed whilecutting in the usual manner; a mining drum hoist 22, preferably mountedon wheels so as to be readily dragged over the mine floor or transportedon a truck on the rails as required; a scraper loading outfit includinga portable loading chute 23 having self-contained power devices thereon,and a scraper apparatus of the above well known form 24 used inconnection with said loading chute; a power drill for forming powderholes; and a ventilating blower fan 26 equipped with till severallengths of flexible tubing. 27 of sufficient length to be extended tothe working face so as to displace with fresh air any smoke or gasesencountered during, the cutting, shooting and loading operations in theclosed ends of the two entries.

The portable hoist 22 is suitably disposed at one side of track stub Tin line with the main haulage track 14, as shown in Figure 2, and isremotely controlled from the scraper loading chute 23 by the scraperloader operator. The undercutting machine 20 is run to the end of one ofeither one of the stubs T 9 or T where the initial cutting operationsare to be commenced, in the form shown in Figure 2, the lower entry 11being chosen for this purpose. The cutting apparatus is unloaded fromthe end of stub T by taking the mining machine off its truck 21 and thenplacing the truck 21 at one side of the stub T as for instance, closelyadjacent the pillar 12, as shown. The loading chute 23 is then put intoloading position on the stub T so as to discharge loads of materialbrought thereupon by the scraper 24 into mine cars suitably positionedupon the main loop 15, as shown in Figures 2 and 3.

A string of empty mine cars, commonly termed a trip, is brought into themine along the haulage track 14 and around the forward end of the loop15 into the opposite entry 10. Since this loop 15 is relatively long,that is, from two hundred to two hundred fifty feet or more, said loopprovides sufficient storage for a large number of empty cars.

Cutting operations are commenced along approximately one half of thewidth of the working face 17 by use of the undercutting machine 20,which cuts a k-erf in the usual manner extending approximately twelvefeet in length from the Wall or rib of the pillar 12, and to a depth ofapproximately seven feet. Thereafter the coal overlying this undercutportion is drilled, shot down, and loaded into the scraper 24 at theworking face, from whence it is conveyed to the mine cars and loadedthereon over the inclined chute 23, in the usual manner. The loading outof one undercut portion, as described, forms a new working face 17substantially twelve feet in length as indicated in Figure 2. Thisworking face is again undercut, shot, and loaded out with the scraperand this operation is repeated until, a narrow entry about twelve feetwide is extended the full depth to which the entry is to be advanced inone stage, that is, up to the next predetermined break through 13(a'distance of about two hundred to two hundred fifty feet), and aboutfifty feet therebeyond, as indicated by dotted lines 17", 17 indicatingthe side walls of the first-mined area, and 17 c the end Wall of thismined area.

It will be understood-of course, theselast named mining operationscontemplate only AB, in'Figures 3 and 4, the scraper 24 be ing operatedin this relatively low-roof area.

At this stage only one-half of the full width of one entry has beenmined. The remaining half is then mined out by making a series ofundercuts along the outer side Wall 17 for the full length of thepreviously advanced narrow portion, as indicated in Figure 2. For thispurpose an ordinary shortwall machine having a cutter bar of six toseven feet in length can, cut to the full width of the room in twosuccessive slabbing outs. After each cut of course, the coal is shotdown and loaded out by the scraper 24. In this case however, the scraperis movable longitudinally of the pile of loose coal shot down from theface, as clearly indicated in Figure 5, which indicates the position ofthe loose coal on the floor after one slabbing underout has been madeand the face prepared for loading. It is manifest from this figure thatthe second slabbing out following the loading out of the loose coal fromthe first cut would complete the undercutting for the full predeterminedwidth of the entry 11, and the loose coal shot down after thesecond'underout can also be loaded out by means of the scraper. In orderto control the movement of the scraper during the loading operationswhere the scraper is moved in a line off-set from the center line of theloading chute 23, as shown in Figure 5, I prefer to use a scraperapparatus including a third rope control line 30 having a sheave 31which engages the pulling rope 32 of the scraper. This third ropecontrol loading apparatus, with control guide sheave 33 is carried on ajack 34 suitably anchored adjacent the rib in the far corner of theworking face 17 and the outer wall or rib of the entry 11, as shown inFigure 5, and the path of movement of the scraper 24 may thus becontrolled by shortening or lengthening the third rope control line 30as desired. I also find it preferable to provide an auxiliary deflector35, which may be of any suitable form, adjacent the outer side of thechute 23, in order to assist the movement of the scraper when it isapproaching the chute at an angle. In the form shown this deflector 35may consist of an ordinary length of track rail anchored by jacks 35 35The purpose of providing an initial fifty foot advance of the entries10, 11, beyond each break through 13 will now be understood whenattention is directed to the desirability of providing a relatively longlead between the loading chute 23 and the control line 30 so that thescraper may always approach the loading chute at a relatively smallangle. In practice, a lead of about fifty feet is found best suitedwhere the width of the entry is about twenty-four feet.

The opposite entry may now be mined out in a similar manner, beginningwith a narrow tunnel one-half the entry width and formed in line withthe track stub T along the pillar 12. It will be understood however,that either entry may be mined out first, as desired. At any suitabletime after the point of the next break through 13 has been reached, saidbreak through may be cut through as for instance, from opposite sides ofthe pillar, although under many conditions, as an intermediate step ofthe method it may be found preferable to utilize the alternative methodshown in Figures 8 and 9, as will be hereinafter more fully set forth.

During the loading operations above described the cars may be moved bymeans of the portable hoist 22 and cable along the track and outwardlytoward the main line 14. as fast as they are loaded. The loaded cars maybe hauled from the mine by means of mine locomotives at any desiredinterval without causing any delay in thecutting and loading operations.

When both entries have been developed to their full widths and have auniform line of advance fifty feet beyond the next breakthrough 13 (inline with lines 17 of Figures 2 and 5) the two entries are then preparedfor advancing the track loop to a new position, with the forward end ofone loop extending through the new break through 18. The miningapparatus, including the cutting machine, scraper loading apparatus,etc., are withdrawn to a suitable position removed from the advancearea, and the work of bringing up the tracks proceeds as follows:

Where, as in the typical conditions illus-' trated, the mined areabeyond the last break through 13 is of such limited height as toprohibit the use of mine cars therein, it is necessary, as the nextstep, to brush the roof or take bottom along the new layout for thetrack loop, so as to increase the height A-B to height AC through thenew break through 13 and along the outer walls of the two entries 10 and11. In the preferred method shown the necessary height is obtained bybrushing the roof. The waste rock resulting from this brushing work isthrown over and disposed in the new gob area 12 as close to the centerlateral pillar as practicable.

The surveyor then lays out a series of sight lines and location pointsby means of which the position of the track can be located, these sightlines and points being most conveniently marked upon. the roof of themine, as for instance, as indicated at P P P and P, etc., in Figure 1.The hoist 22 is dragged forwardly along on track or bottom of eithernvoaess of the entries 10 and 11 to a new position just beyond the lastbreak through. In Figure 1 said hoist is shown in full lines in thelower entry 11 substantially in line with the points P and P which markthe center line of the main haulage track 14:. The hoist is preferablyadvanced to this position under its own power by anchoring the free endof the cable anddragging said hoist over the mine bottom to its newposition. lVith the hoist in such position, the several sections of thetrack loop 15 are then detached from each other, and the sectionsdisposed in the two entries are dragged forwardly to their new positionsby means of the hoist cable.

Details of construction of certain typical track sections are shown inFigure 6, which is an enlarged View showing three sections T T and Tforming the switch connections from the main track to the stub track T".Figure 7 illustrates the details of another combination of tracksections T and T together constituting a single curve radius at onecorner of the track loop 15. As will be seen from these figures, as wellas from the general layout illustrated in Figure 1, the s veral tracksections are arranged so that they may be taken apart, drawn forwardlyto a new position along their respective entries and replaced with theaid of sighting points P P P, etc., without the necessity of employingskilled track layers, the sections being provided with exact locationmarks, as for instance, point P of sections T 0nd T (see Figure 7) sothat said sections may be readily relocated by dropping a plumb linefrom the corresponding point P previously located by the surveyor on theroof of the mine. Similarly, other sections of the track are providedwith point marks, such as P P, P and P, so that the track sections maybe all readily located and connected in their new positions.

It will be observed further that the sevoral track sections are suitablymarked and fitted together in such a manner that they can only berejoined together in proper order. For instance, sections T and T*,which otherwise might be similar to sections T and T are distinguishableby a different position of their respective location points P and P sothat these two curve sections are readily identified and put in theirproper positions. Similarly, the switch made up of parts T', T and Tshown in detail in Figure 6, is of different curvature from the switchsection made up of parts T and T and are further identified by means ofthe location points P and P. It will be understood of course that thespecific arrangement and proportions of the several divisions of tracksections may be varied somewhat from that illustrated herein, as well asthe specific arrangement of predetermined location points appliedthereto, but I consider it to be novel to provide a track loop made upofa plurality of track sections which may be detached and replaced in anadvanced position with the aid of predetermined location points, asherein disclosed.

It-will be understood of course, that the hoist 22 which is usedto drawup the separate sections of track, may be located in either entry andthetrack sections moved by means of the cable and various arrangements ofguide sheaves therefor, as are necessary.

Thus, in Figure 1, the hoist is shown in full 7 lines in entry 11 and inanother possible position (in dotted lines) in entry 10.

After the track has been relocated and carried forward to a new positionas shown in Figure 1, it is usually desirable to set the posts or props12 around the gob areas 12, 12, so as to support the roof along thebrushed trackway as shown in Figures 3 and 4. With the track laid andposts set as described, a full cycle of mining operations will then havebeen completed, ready for bringing the mining apparatus in for a newcycle of cutting and loading operationsin order to advance the workingfaces 16 and 17 as before.

Figures 8 and 9 show an alternative step in the method of advancing theentries 10 and 11 which may be used to speed up productionunderfavorable conditions. In mining out the advance breakthrough 13,from entry 11, instead of stopping at the midpoint of the pillar 12 ashas been above described (see Figure 5) said breakthrough is extendedthrough the pillar 12 to a point about twelve feet beyond from saidpillar, which is equal to the width of the initial development tunnel asis illustrated. at 17, Figure 2. After said breakthrough and extensionthereof has been cut and the loose coal has been removed therefrom bymeans of the scraper 24in the usual manner, a nest 13 is formed at rightangles to the break through 13 in an advancing direction. The loose coalis again removed from thenext 13 bymeans of the scraper 24 in the usualmanner as illustrated in Figure 8. It should be noted that whenremovingmaterial from the breakthrough 13 and nest13 that the scraper 24 isloaded by hand where it is not possible for said scraper to gather itsown load, and that the control rope 31 enables the scraper to turn fromthe break through to the heading 10 at right anglesthereto so said loosecoal may be loaded in'the mine cars in the usual manner as hashereinbefore been explained.

The break through 13 and nest 13 being mined out, the tracks 14 areextended and a curve is laid to said break through. An extra section oftrack T is laid into said break through. The curve is madeup of switchsections T and T exactly the same as the sections T and T is placed atthe preceding break through 13 laid in the same manner as said precedingsections by aid of a similar set of sights. After this track has beenlaid the top is shot down and the rock loaded on mine cars and hauledaway.'

Simultaneously with the extension of the track 14 and shooting andloading of rock from the break through 13 and nest 13, the heading 11may be advanced in the same manner as the heading 10 is advanced and ashas hereinbefore been described, so that when said heading connects withthe break through 13 and nest 13 the rock has been removed from the topinsaid break through and next to make headroom for mine cars and thescraper loader apparatus 23.

This alternative system, while requiring additional sections of trackand a crew of men to shoot and load the rock while the opposite entry isbeing cut, is particularly advantageous in that it provides a meanswhereby the rock work in one entry and break through may be completedwhile the other entry is being mined out and thus it eliminates delayswhich would necessarily result if each entry or heading were to be minedout and the top brushed separately. From the above described miningsystem and apparatus used it will be seen that several novel andadvantageous features deserve especial emphasis. Among these featuresmay be mentioned the following, in the order in which they, appear inthe cycle of operations just described:

1. The initial cutting and loading operations advancing in limited widthalong the inner sides of the entries 10 and 11 and adjacent the centerpillar 12 affords several advantages. On account of the comparativelylimited width of the initial penetration, the danger of roof falls arecorrespondingly limited until after the initial entry is widened out bythe longitudinal slabbing cuts. When any roof falls occur adjacent theillar they are not likely to seriously interfere with the cutting andloading operations as such rock as does fall from the roof adjacent thepillar can be placed in the gob area 12 with one handling and thereforedoes not require a second handling. A further advantage of this methodis that it provides a relatively long working face for the two or moreslabbing cuts (two or three hundred feet in length) which can both becut and loaded out more rapidly than if the entire length of the workingfaces 16 and 17 were advanced in one operation.

As a rule any bad roof has a tendency to show up more quickly near theribs of the entry while cutting the narrow tunnel and will develop andfall when these longitudinally extending slabbing cuts are made, buteven if roof does fall it can be disposed of in gob area 12 withoutrehandling. This slabbing out also gives a cleaner and straighter siderib or wall than would be the case if the entire width of the entries 16and 17 were advanced by a series of relatively short advance cuts as inordinary shortwall operations.

2. The use of a scraper loader gives particularly advantageous resultsin the economical operation of my inproved system due to itsadaptability to low roof conditions, and particularly where the thirdrope control line 30 is used for controlling the path of movement of thescraper along the coal face and cleaning up the loose material from theslab bing cuts along the outer walls of the entries.

3. The use of a complete track loop 15 extending through adjacent breakthroughs and providing ample storage space for cars which serves equallythe. loading apparatus in both entries, is also particularlyadvantageous inasmuch as this arrangement permits the cars to be handledby means of a. sin gle hoist and cable without the necessity of aseparate locomotive for switching or moving the cars as they are beingloaded. This arrangement of loop track ordinarily gives stora e spacefor enough mine cars to handle all of the coal, loaded out during oneshift or period of working hours so it is not necessary to couple up thehaulage locomotive more than once in an entire shift for the purpose oftransporting loaded coal away from the area of mining operation. Inshort, this improved track system aids in solving one of the chiefshortcomings inherent in most min-- ing systems, viz, that of providinga sufficient and constant supply of empt 7 cars so as to permitsubstantial continuous operation of the cutting and loading apparatus.In my improved system employing a looped track, the loading operationsare therefore entirely independent of any of the delays usuallyoccurring in the transportion of haulage systems for supplying entriesor removing loaded cars from the area of mining operations.

4. The arrangement or layout of advancing development including the gobarea 12, im mediately adjacent the center pillar 12 is also ofconsiderable importance in the econom es claimed for the use of myimproved mining system inasmuch as it entirely eliminates the necessityfor transporting waste rock removed by brushing, etc. In my improvedsystem this rock is deposited in the gob areas immediately to one sideof the brushed areas, and therefore does not have to be transported inmine cars for proper disposal. This saving in labor and transportationcosts alone represents a substantial item ordinarily added to the costof low coal extraction.

5. In will be observed further that especial provisions are made forsafety of the miners, through the several stages of the operations abovedescribed.

, 6. This system of development is usually worked on the night shift asloading machines can be worked without the extra cost of a motorman andhelper to handle the cars since said cars may be placed in the loopduring the day shift and these cars will be ample to run the nightshift.

I claim as my invention:

1. In a coal mining and loading system, the method of advancing a pairof parallel entries on opposite sides of a pillar with breakthroughsconnecting said entries at predetermined intervals, which consists indriving an initial tunnel along the inner side of one of said entries ata width substantially less than its final width, said initial tunnelextending substantially beyond the next predetermined point ofbreakthrough, and widening said initial tunnel along its outer face toits full width, then driving an initial tunnel of similar width andlength in the adjacent entry, and widening the same in a similar manneralong its outer face, extending and placing portable continuous looptrack around said pillar and through the next advance break through bymeans of predetermined sight points and loading loose material from bothentries into mine cars stored on said loop track during the nextsucceeding cycle of advancing said entries.

2. In a coal mining and loading system, the

method of advancing a pair of parallel entries on opposite sides of apillar with breakthroughs connecting said entries at prede terminedintervals, which consists in driving an initial tunnel along the innerside of one of said entries at a width substantially less than its finalwidth, said initial tunnel extending substantially beyond the nextpredetermined point of breakthrough, and widening said initial tunnelalong its outer face to its full width, then driving an initial tunnelof similar width and length in the adjacent entry, and widening the samein a similar manner along its outer face, brushing or removing rock fromthe roof of the mine in each of said entries along its outer wall anddepositing said rock directly in a gob area along the side of theadjacent pillar, extending and placing portable continuous loop track inthe brushed portions around said pillar and through the next advancebreakthrough by means of predetermined sight points, and loading loosematerial from both entries into mine cars stored on said loop trackduring the next succeeding cycle of advancing said entries.

8. In a coal mining and loading system, the method of advancing a pairof parallel entries on opposite sides of a pillar with breakthroughsconnecting said entries at predetermined intervals, which consists indriving an initial tunnel along the inner side of one of said entries ata width substantially less than its final width, said initial tunnelextending substantially beyond the next predetermined point ofbreakthrough, and widening said initial tunnel along its outer face toits full width, the loose material from said initial tunneling andWidening operations being removed and loaded on to mine cars by ascraper loader arranged for movement longitudinally of said entry, thendriving an initial tunnel of similar width and length in the adjacententry, and widening the same in a similar manner along its outer face,extending and placing portable continuous loop track around said pillarand through the next advance breakthrough by means of predeterminedsight points and loading loose material from both entries into mine carsstored on said loop track during the next succeeding cycle of advancingsaid entries.

at. In a coal mining and loading system, the method of advancing a pairof parallel entries on opposite sides of a pillar with breakthroughsconnecting said entries at predetermined intervals, which consists indriving an initial tunnel along the inner side of one of said entries ata width substantially less than its final width, said initial tunnelextending substantially beyond the next predetermined point ofbreakthrough, and Widening said initial tunnel along its outer face toits full width, the loose material from said initial tunneling andwidening operations being removed and loaded on to mine cars by ascraper loader arranged for movementlongit-udinally of said entry andloading at a single point adjacent the pillar, then driving an initialtunnel of similar Width and length in the adjacent entry, and Wideningthe same in a similar manner along its outer face, extending and placingportable continuous loop track around said pillar and through the nextadvance breakthrough by means of predetermined sight points and loadingloose material from both entries into mine cars stored .on said looptrack during the next succeeding cycle of advancing said entries. v

' 5. In a coal mining and loading system, the method of advancing a pairof parallel entries on opposite sides of a pillar with breakthroughsconnecting said entries at predetermined intervals, which consists indriving an initial tunnel along the inner side of one of said entries ata width substantially less than its final width, said initial tunnelextending substantiallybeyond the next predetermined point ofbreakthrough, and widening said initial tunnel along its outer face toits full width, cutting the next breakthrough and extending itoveralimited area in line with the opposite entry, brushing or removingrock from the roof of said mine in an area along the outer wall of saidfirst entry and through said breakthrough, extending a length of trackalong such brushed areas for loading out further advance Work along saidfirst entry while proceeeding to drive an initial tunnel of similarWidth and length in the adjacent entry, and widening the same in asimilar manner along its outer face, extending and placing portablecontinuous loop track around said pillarand through the next advancebreakthrough by means of predetermined sight points and loading loosematerial from both entries into mine cars stored on said 100p trackduring the next succeeding cycle of advancing said entries.

Signed at Chicago, in the county of Cook and State of Illinois, this 4thday of February, A. D. 1928.

LOYAL F. CRAWFORD.

